Hitomi Kawaida, Kohki Ohba, Yuhki Koutake, Hiroshi Shimizu, Hidenori Tachida, Yoshitaka Kobayakawa, Symbiosis between hydra and chlorella: Molecular phylogenetic analysis and experimental study provide insight into its origin and evolution, http://dx.doi.org/10.1016/j.ympev.2012.11.018, 66, 906-914, 2013.02, Although many physiological studies have been reported on the symbiosis between hydra and green algae, very little information from a molecular phylogenetic aspect of symbiosis is available. In order to understand the origin and evolution of symbiosis between the two organisms, we compared the phy- logenetic relationships among symbiotic green algae with the phylogenetic relationships among host hydra strains. To do so, we reconstructed molecular phylogenetic trees of several strains of symbiotic chlorella harbored in the endodermal epithelial cells of viridissima group hydra strains and investigated their congruence with the molecular phylogenetic trees of the host hydra strains. To examine the species specificity between the host and the symbiont with respect to the genetic distance, we also tried to intro- duce chlorella strains into two aposymbiotic strains of viridissima group hydra in which symbiotic chlo- rella had been eliminated in advance. We discussed the origin and history of symbiosis between hydra and green algae based on the analysis..